Echo ranging and identification system



Feb. 26, 1952 Filed June 15, 1945 A. A. VARELA ECHO RANGING AND IDENTIFICATION SYSTEM 2 SHEETS-SHEET l RADIO ECHO IDENTIFICATION IDENTIFICATION IMPULSE ggg sg'g lMPULSE SIGNAL TRANSMITTER TRANSMITTER RECEIVER KEYER A SIGNAL CHANNEL 6 /5 CONTROL A V OATHODE TRIGGER f /9 V Tim/E R urr c SIGNAL CHANNEL /7 CONTROL J SWEEP GENERATOR /IO M DELAY GENERATOR 01 H H H J;L1..r;5 3

T b v l l l' c it I gwuu/wfob b5 I I A. A. VARELA Feb. 26, 1952 A. A. VARELA ECHO RANGING AND IDENTIFICATION SYSTEM 2 SHEETSSHEET 2 Filed June 13, 1945 A. A. VARELA v W I-1a Patented Feb. 26, 1952 ECHO' RANGING AND IDENTIFICATION SYSTEM Arthur'A. Varela, Washington, D. 6.

Application June 1-3, 1945, Serial No. 599,289

(Granted under the act of March 3, 1883, as" amended April 30, 1928'; 370 G. 757) 12 Claims.

This invention relates to echo ranging and obstacle identification systems, and is particularly directed tothe problem of coordinate operation of such systems;

In echo ranging systerzs a transmitted impulse is reflected from an obstacle, and the elapsed time between transmission and echo reception is employed to determine the range of the object. Normally a radio frequency electromagneticimpulse is employed, and the transmitted or refiected signals are directly indicated on a cathode ray tube time base.

Obstacle identification systems include an interrogating impulse transmitter, and a receiver together with a transmitter servile thereto installed on the obstacle. The latter unit, the transpondor, is operative responsively to a received signal from the interrogator to emit a signal which identifies the obstacle. The signal maybe: coded as desired, but in a simple system a selected time delay between the reception of theinterrogator impulse and. the transmission of a response impulse is sufficient to yield an adequate amount of information. The response impulse; is detected by a local receiver.

In many situations it is necessary to correlate the information received from the echo ranging installation with that received on the identification. system. In particular, this is true where one of a number of obstacles indicated by the echo ranging system is transmittingan identification signal. Through the employment of the present invention, it is immediately manifest to the operator which of the obstacles indicated is emitting the identification signal.

It is accordingly an object of the invention to provide for coordinate operation of the echo ranging and recognition systems.

It is another object of the invention to provide a. common indicator for echo ranging and identification. systems.

This invention will be further. described with reference to the drawings, in which:

Figure 1 shows in block diagramanexemplary system. of the present, invention,

Figure 2. shows in circuit diagram the coordinating componentsof the present invention, and

Figure 3' shows wave forms present atvarious operating points inthe diagram of Figure 2..

In. the embodiment, shown in Figure 1 a. radio echo system is used. This comprises animpulse transmitter l and radio echo receiver 2. This system may be of any conventional type, and is employed without change in the present 00- ordinatedinstallation.

The invention alsocontemplates the use of an identification system including an impulse transmitter 3, and identification response signal receiver 4.

The present invention coordinates the operation of the identification system with that of the 2 radio echo ranging system, and simultaneously indicates the information received on both systems upon the f'ace of a single cathode ray tube.

This is effected by'op'erating the identification impulse transmitter alternate operations of the echo ranging impulse transmitter. This operation is obtained under control of a signalgenerated in the echo ranging transmitter. In the system shown,- this transmitter includes a keying" circuit and this keying circuit is employed to: originate a control signal for the identificationsystem. The latter is fed into a trigger circuit, or frequency divider, which is operative to generate control. signals in two separate channels.

The signals in one channel correspond to one series of alternate transmitter impulses.- and the signals in the other channel coincide with the intervening series of alternate transmitter impulses.

The system includes a cathode ray tube 6 and a sweep generator 7 therefor. The latter may generate a linear sweep, and is operative responsively to an injected pulse.

In the series of impulse transmissions during which echo ranging information is applied to" cathode ray tube (i a control signal from trigger circuit 5 operates" directly on sweep generator 1, and simultaneouslyefiects application of the echo signals from receiver 2 to the cathode ray tube through a signal channel control device 8.

1nthe other series of alternate impulse transmissions, during which the identification impulse transmitter is operated and the identifi-- cation signal receiver information is applied to cathode ray tube 6; the other output channel of trigger circuit 5 keys offthe identification impulse transmitter 3', applies the identification receiver output to cathode ray tube 6 through operation of the signal channel control means 9', and also trips off the cathode ray tube sweep generator I through the operation of a delayed signal generator I01 Delayed signal generator ll) is employedfor'the purpose-of aligning the sweep position of the identification signal with that of the" radio echo ranging system signal. As pointed out above, the transponder unit may emit an identification response signal with a coding time delay. This delay may be compensated by the This constitutes the master control signal, which controls operation of the entire circuit shown in Figure 2. The signal introduced at terminals l5 effects operation of a trigger circuit comprising two vacuum tubes, I6 and I1. These two tubes are connected for alternate conduction in a re generative trigger circuit. A positive voltage source H3 is supplied for energizing anodes I9 and screen grids of the tubes, and negative voltage source 22 is provided to supply negative bias for control grids 23. Cathode 24 of tube I6 is returned to ground through cathode resistor 25, and cathode 26 of tube I1 is returned to ground through cathode resistor 21.

The operation of the circuit including tubes i5 and I! is such as to transfer conduction from one tube to the other upon the introduction of a positive impulse voltage to the control grid of the non-conducting tube. This impulse voltage is introduced at each operation of transmitter Therefore tube i6 will be in conduction during alternate impulse transmitter operation cycles, tube I! will be in conduction during the intervening series of cycles, and the trigger circuit may be employed to supply the desired control voltages for the components shown in Figure l.

Cutofi? in tube I! is employed to supply a trigger voltage to the identification impulse transmitter 3. For this purpose the positive anode swing accompanying cutoff in tube I7 is differentiated through condenser 30 across resistor 3|, and. is applied to control grid 32 of cathode follower tube 33. The output of this cathode follower tube 33, which acts as a low impedance source, is then applied to control grid 34 of a second cathode follower tube 35. The output of tube 35 is applied at terminal 36, which maybe connected to the identification impulse transmitter for keying the same on one series of alternate radio echo ranging impulse transmitter operation. By driving cathode follower 35 from follower 33, the grid of the output tube may be driven into grid conduction operation to supply substantial voltage signals across a low impedance load. It will be understood that the negative impulses introduced to grid 32 upon conduction of tube II, have substantially no effect at terminal 36, since both this negative impulse and the resulting smaller negative impulse applied at control grid 34 do not result in any such magnitude of voltage delivered at terminals 36. Also, identification impulse transmitter 3 will be suitably constructed so as not to be responsive to negative input voltages.

The positive'swing of the anode of tube l1 accompanying cutoff is employed additionally for operating the delay generator l0, which comprises tubes 40 and 4|. These tubes are arranged for alternate conduction, but tube 4| is normally maintained in conduction by application of a positive voltage on its control grid 42 through resistor 43 connected to anode 44 of tube 40. Control grid 45 of tube 46 is connected to anode 41 of tube 4| through a coupling condenser 46. Condenser 46 is of a rather substantial value. Control grid 45 of tube as is also connected to the anode of tube I? through series resistor 48 and adjustable voltage divider 49. The time constant of grid 45 is determined by condenser 46 in combination with series resistor 48 and the adjustable voltage divider 2-9. Accordingly, when the anode l9 swings positive, grid 45 also moves positive at a rate depending upon the setting of voltage divider 49. It is apparent therefore, that tube 4|! will go into conduction a selectable time after tube cuts off. The divided control maybe calibrated directly in the delay time i 12 of cathode follower tube 55.

4 which is effected by the circuit. The feedback from tubes 4| to tube 66 through condenser 46 causes a rapid shift in conduction between the tubes. This supplies a positive output voltage at anode 47 of'tube 4|.

The delayed positive voltage swing supplied at anode 4'! tube 4| is difierentiated through condenser 5| and resistor 52. The positive voltage pip thereby generated is applied at control grid 53 of tube 54. This tube is connected as a cathode follower in parallel with tube 55. Their output is supplied to terminal 56 for the purpose of connection to the sweep generator 1 shown in Figure 1.

It will be understood that the negative voltage pip applied to control grid 53 of tube 54, accompanying reestablishment of conduction in tube 4|, does not effect operation of the sweep generator 1. i

In the circuit of Figure 2 the output of the identification signal receiver 4 is applied at terminal 56 to tube 6|. Operation of tube 6| is con trolled by the bias voltage developed across its cathode resistor 62, and for this purpose cathode 26 of tube I7 is coupled to resistor 62. Consequently, cathode 63 of tube 6| is maintained at a relatively high positive bias during conduction of tube IT, so that tube 6| is effectively blocked during this period. Upon cutoff of tube H, the bias developed across cathode resistor 2'! falls to zero and consequently the cutoff bias applied to tube 6| is removed. During the ensuing period in which tube I! is non-conducting, the signal applied at terminal 60 to the grid of tube 6| is suit ably amplified and applied to tube 65. The signal developed at anode 66 of tube is delivered at terminal 67 for application to a deflection electrode of cathode ray tube 6.

In an embodiment of the invention wherein the sweep signal developed by generator I is applied to the horizontal deflecting plates of a oathode ray tube, the signal developed at terminal 6'! may be applied to the vertical deflection plates, so that the output of the identification signal receiver 66 is developed on the time base as a vertical deflection. Where a positive identification signal is applied to tube SI at terminal 60, a positive voltage will be supplied at output terminal 61.

The positive swing of anode I 9 of tube I 6 which accompanies cutoff of this tube constitutes the signal for keying sweep generator I in synchronism with the echo ranging impulse transmitter and for applying the output of the radio echo signal receiver to the cathode ray tube. For this purpose the positive swing of the anode H! of tube I6 is differentiated through condenser 10 and resistor 1| for application to control grid The output .of this tube is applied at terminals 56 for connection with the sweep generator wherein it acts as triggering voltage.

The output of the radio echo receiver is ap- -1 plied at terminal 15 for introduction to control of tube l? is applied 1 as cathode-- modula'tiorito" tube l8; which isprovided with a grounded grid.-

The'output of tube 78-is developed across anode a negative signal at terminal 91 for application'- to the cathode ray tube indicator;

In addition to providing for deflection in theopposite' sense of the radio echo signal and-theidentification signal, it maybe desired to'separate the cathode ray tube traces upon which these signals are superimposed. This may be accomplished'by efiectingdifferent conducting conditions in tubes I8 and 61, through which tubes the respective signals are applied to tube 65. In the embodiment shown in Figure 2, this result may be. obtained by controlling the cathode biasing ofithes'e two tubes. To this end the combina tion of resistors 62 and 2? in parallel may be made of considerably higher value than the combination resistance of cathode resistors 25 and 801 In this case more bias will be present on tube 6i during its transmission than is present on tube 78 during the latters transmission. This results in the effective application oi a positive bias on the control grid of'tube 65 during the conductionperiod of tube 6|. This positive voltage will be communicated at terminal 5'! for application to the vertical deflection plates of the cathod ray tube, and-consequently will produce a separation 2, the echo ranging indication pattern remains geometrically fixed on the face of theindicator tube. Aligned therewith appears the time base line for the identification indications, but this-in-' dication pattern may be adjusted along its baseline and relative to the fixed echo indications. Consequently a transparent range scale may beemployed' overlying the echo indications without loss of its zero calibration on adjustment of the identification signal position. a

The control voltage waveforms present at varii ouspoints iii-Figure 2 are shown diagrammatically in Figure 3. At a is indicated the recurrent pulse supplieclat terminal [Efrem the radio echoiinpulse transmitter i. The'v'cltage developed at anode E9 of tube I6 is shown at b, and I the voltage developed at anode I 9 of tube IT is' shown at c. The voltage developedat cathode- PA of tube It is shown at cl, and that of cathnde 25 of tube I! is shown at e. At 1' is shown the difierentiated voltage signal derived from b, this pulse signal being applied to control grid 32 of tube 33 for keying the identification impulse transmitter. At 9 is shown the voltage supplied to control grid 53 of tube 54. This voltageis obtained by differentiating the ouimut of the delay multivibrator, and is derived from anode ll of tube 4|. At h is shown the voltage delivered for keying the sweep generator T, which is delivered at terminal 55. This signal comprises the combined outputs obtained by differentiating the signals at anode 61 of tube 41 and anode IQ of tube IS. The blocking voltages applied to the signal transmission tubes Ti and E! are as shown respectively at d and e. These tubes transmit with zero applied control i. voltage} and are blocked: on" a positive: lnjective voltage.-

Ii'r will be under'stood thatthe embodiment de-:

scribed is exemplary of the-invention, and that the-limits thereof 'will be ascertained by reference to the appended-claims:

The invention described herein may be manufac'tiired and-us'ed by or for the Government of the Un'ited states of- America for governmental pii-rpose"swithout thepayment of any royalties therwn or'therefor.

l. combination, a radioecho-ranging systern" having recurrentlyoperative impulse transmitter, an-echdreceiver, an identification system having" an impulse transmitter and a signalreceiver, -mea'nsoperative in dependency on the radio-echosystem to operate said identificaticn impulsetransmitteron alternate operations of meeehorangingimpulse transmitter, and a cathode'rav tube indicator responsive to both said systemsalternately to-inclicate-the' responses of both sa id receivers Z In combination; aradio echo ranging sys-' tern having a rccurren'tly operative impulse transmitter andan echo'receiver, an identification system havingan impulse transmitter and a signalre'ceiver; meansoperative in dependency on the radioecho system tooperate said identification impulse" transmitter on alternate cycles of the echo ranging'impulse transmitter, a cathode ray tube indicator-"systemresponsive to both said receivers to indicate" their outputs along juxtaposed time base. loci, andmeans operativeto" adjustablyposition' the identification receiver response along it'stiinin'gbase locus;

3; In" combination; a radio echo-ranging system having a" recurrently operative impulse transmitter" and? an echo receiver, an identificationsyst'em having an impulse'transmitter and a signal, receiver, means" operative 'in dependency on the; radio echo system" to operate said identification, impulse transmitter on alternate cycles of'jthe'je'cho ranging impulse transmitter, a cathod'e'fra'y tube responsive tb both said receivers to indicate their outputs along juxtaposed time base loci, and means operative" to adjustably position theideritification'receiver response along its timing basewhile' maintaining the echo receiver response's'tationary on its" time base;

4'. In combination; a radio echo ranging systeiri, having a, recurrently operative impulsetransmitter and an echoj receiver, an identification system having an impulse transmitter and a signal receiver; means operative'in dependency on theradio' echos'ystein to operate said identifica'tiorl impulse transmitter on alternate cycles of the echolrarig'ing'f i ftilils e, transmitter, a cathode ra'y ti ilie';v a; sweep", g' aerator therefor, means for ti'ipping said sweepfin alternate cycles in adjustable". relation to the identification impulse transmitter." operation,- means for tripping said sweep in. dependency on the radio echo impulse transmitter in the other series of alternate cycles,

and. means for selectively. applying. the receiver outputs to saidtube.

5. In combinatiomara'dio echo ranging system having. areOurr'eritIy operative, impulse transmitter andan echo receiver, an identification system having an impulse transmitter and a signal rece'iver'; a pair of "tubes arranged for alternate conduction control means for said tubes operativef to shift oondu'c'tionj from one to the other, in depen ency: on radio echo impulse transmitter'o'perati'on; a cathode ray" tube, a sweepgenerator therefor, means responsive to conduction in one of said pair of tubes operative to trip said identification impulse transmitter, means responsive to conduction in said one tube to trip said sweep generator, means responsive to conduction in said one tube to apply the output of the identification signal receiver to the cathode ray tube, means responsive to conduction in the other of said pair of tubes to trip the sweep generator, and means responsive to conduction in said other tube to apply the output of the radio echo receiver to the cathode ray tube.

6. In combination, a radio echo ranging system having a recurrently operative impulse transmitter and an echo receiver, an identification system having an impulse transmitter and a signal receiver, a pair of tubes arranged for alternate conduction, control means for said tubes operative to shift conduction from one to the other in dependency on radio echo impulse transmitter operation, a cathode ray tube, a sweep generator therefor, means responsive to conduction in one of said pair of tubes operative to trip said identification impulse transmitter,

means responsive to conduction in said one tube to trip said sweep generator after an adjustable time delay, means responsive to conduction in said one tube to apply the output of the identifi cation signal receiver to the cathode ray tube,

,means responsive to conduction in the other of said pair of tubes to trip the sweep generator,

and means responsive to conduction in said other tube to apply the output of the radiov echo, receiver to the cathode ray tube. 1

7, In combination, a'radio echo ranging sys-' tem having a recurrently operative impulse transmitter, and an echo receiver, an identification system having an impulse transmitter and a signal receiver, a pair of tubes arranged for alternate conduction, control means for said tubes operative to shift conduction from one to the other in dependency on radio echo impulse transmitter operation, a cathode ray tube, a sweep generator therefor, means responsive to conduction in one of said pair of tubes operative to trip said identification impulse transmitter, means responsive to conduction in said one tube to trip said sweep generator, means responsive to conduction in said one tube to apply the output of the identification signal receiver to the cathode ray tube along one locus, and means responsive to conduction in said other tube to apply the output of the radio echo receiver to the cathode ray tube alon" another locus.

8. In combination, a radio echo ranging system having a recurrently operative impulse transmitter and an echo receiver, an identification system having an impulse transmitter and a signal receiver, a pair of tubes arranged for alternate conduction, control means for said tubes operative to shift conduction from one to the other in de pendency on radio echo impulse transmitter operation, a cathode ray tube, a sweep generator therefor, means responsive to conduction in one of said pair of tubes operative to trip said identification impulse transmitter, means responsive to conduction in said one tube to apply the output of the identification signal receiver to the cathode ray tube along one locus, and means responsive to conduction-in said other tube to apply the out put of the radio echo receiver to the cathode ray tube along another locus.

9. In combination, a radio echo ranging system having a recurrently operative impulse transmitter and an echo receiver, an identification system having an impulse transmitter and a signal receiver, an assymetric switching circuit comprising a pair of tubes arranged for unequal alternate conduction, a common load circuit fed by the tubes, means responsive to radio echo impulse transmitter operation to shift conduction between said tubes, means for applying the echo receiver output to one of said tubes, means for applying the signal receiver output to the other of said tubes, means responsive to the switching circuit operative to trip the identification impulse transmitter, a cathode ray tube, a sweep generator therefor operative in dependency on the switching circuit, and means for applying the load circuit signal to the tube whereby the echo and signal receiver outputs are selectively indicated .by the tube.

10. In combination, impulse transmitter means, an echo receiver, a signal receiver, an assymetric switching circuit including a pair of tubes arranged for unequal alternate conduction, a com mon load circuit fed by the tubes, means responsive to impulse transmitter means operative to shift conduction between said tubes, means for applying the echo receiver output to one of said tubes, means for applying the signal receiver output to the other of said tubes, a cathode ray tube, a sweep generator therefor operative in dependency on the switching circuit, and means for applying the load circuit to the tube whereby the echo and signal receiver output are selectively indicated by the tube.

11. In combination, recurrently operative impulse transmitter means, an impulse echo receiver, a signal receiver, a cathod ray tube, sweep generator means for saidtube, switching means operative in dependency on operation of the transmitter means to connect one or the other receiver outputs to the tube, and control means for the sweep generator means operative to trip the same in fixed time relation to impulse transmitter operation on connection of the echo receiver to the tube and in variable time relation to impulse transmitter operation on connection of the signal receiver to the tube.

12. In combination, recurrently operative impulse transmitter means, an impulse echo receiver, a signal receiver, a cathode ray tube, sweep generator means for said tube, switching means operative in dependency on operation of the transmitter means to connect one or the other receiver outputs to the tube, and control means for the sweep generator means operative to trip the same in fixed time relation to impulse transmitter operation on connection of the echo receiver to the tube and in variably delayed time relation to impulse transmitter operation on connection of the signal receiver to the tube.

ARTHUR A. VAR'ELLA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,157,122 Dunn-lore May 9, 1939 2,403,755 Rankin July 9, 1946 2,405,930 Goldberg Aug. 13, 1946 2,466,711 Kenyon Apr. 12, 1949 2,471,373 Joyner May 24, 1949 2,515,178 Barchok July 18, 1950 OTHER REFERENCES Radar System Fundamentals, War Dept. Publication TM 11-467, April, 1944. 

